Apparatus for water penetration testing of sole leather



April 10, 1962 I T. J. CARTER APPARATUS FOR WATER PENETRATION TESTING OFSOLE LEATHER Filed Nov. 4, 1959 2 Sheets-Sheet 1 INVENTOR Thomas I (amerEND POIN T mom/1702 ATTORNEY United States Patent Oflice Patented Apr.10, 1962 3,028,755 APPARATUS FOR WATER PENETRATIQN TESTING OF SOLELEATHER Thomas J. (Jarter, Washington, D.C.,, assignor to the UnitedStates of America as represented by the Secretary of Commerce Filed Nov.4, 1959, Ser. No. 851,205 6 Claims. (Cl. 73-100) This invention relatesto apparatus for testing the water penetration of leather andotherflexible materials and more particularly to apparatus for determiningthe resistance of sole leather to water penetration under dynamicconditions. r g V The flexural properties of leather and its ability totransmit water vapor make it a highly desirable material for theconstruction of shoes. However, its porosity causes weak resistance towater penetration and treatments must be applied to leather to improveits water resistive properties. 7

A number of test methods have been used to determine the waterresistance of leather. These methods, however, do not give a reliablemeasure of the water resistance of leather under conditions of use. Forexample, not only does flexing increase the rate of water penetrationbut also the pentration is related to the angle to which a specimen isbent in flexing. V

The subject invention contemplates apparatus whereby the waterresistance :of sole leather is measured; under simulated conditions ofpractical wear and wherein the various factors which influence the rateof water penetration are encountered. Specifically, the apparatusconsists of reciprocating members for flexing the specimen, means forapplying water to and abraiding the underside of the specimen and anelectronic device to indicate the end point of the test. The resistanceto penetration is measured by the number of flexes and/or the timerequired for penetration. The influence of flexing, thickness of thespecimen, location on the leather bend and compression of the specimenupon water penetration and water absorption are determined. In general,the specimen is clamped so that the angle .of bend is approximately 90".For leather specimens having a high resistance to grain cracking,however, adjustment can be made to decrease the angle of the bend andthereby increase the rate of water penetration.

The primary object of this invention is to simulate conditionsencountered by the sole of a shoe in actual service.

Another object of this invention is to provide a flexing mechanism whichwill bend a leather specimen in contact with water at an angle similarto that of a shoe in actual service.

Still another object of this invention is to provide means fordetermining the resistance of sole leather to penetration by water.

Another object of this invention is to provide means whereby the waterresisting effects of various impregnating materials applied to soleleather may be evaluated.

A further object of this invention is to provide means whereby a soleleather specimen may be flexed at various angles of bend.

Other uses and advantages of the invention will become apparent uponreference to the specification and drawings in which:

FIG. 1 is a side elevational view of the water penetration testingapparatus of this invention;

FIG. 2 is a top plan view of the apparatus of FIG. 1;

FIG. 3 is a graph illustrating the percentage of water absorption forflexed and unflexed leather specimens plotted as the ordinate and thetime required for water penetration as the abscissa;

the specimen of FIG. 1 in both flexed and unfiexed posi- 1 tions.

Referring to the drawings, there is shown in FIGS. 1 and 2 a base 10 towhich end panels 11 and 12, respectively, are welded or otherwisesecured. The base 10 and panels L1-12 are suitably constructed of steelplate or the like. The outboard ends of a pair of spaced parallel tracks15a- 15b pass through bores in end panels 11 and 12 and are detachablysecured thereto by screws 16 which pass through recesses in the sidepanel portions as best seen in FIG. 1 of the drawings. In a preferredembodiment of the invention, the tracks 15a15b are spaced approximately7 inches apart Whereas end panels 1 1i2 are approximately 14 inchesapart.

Assemblies 13--14, to which a test specimen is secured in a mannerhereinafter to be discussed in detail, are slidably mounted on tracks15a15b. A pair of cylindrical bearings 13a13b, such as are well known inthe art, are integrally mounted within the upper portions of theassembly 13; in like manner, bearings Miai th mount within the upperportions of the assembly 14. The track 15a is journaled in the bearingsfizz- 14a, likewise, track 15b is journaled in bearings 13b14b.

The assembly 13 is reciprocally driven by a ratiomotor M which ispreferably geared to operate at 30 cycles a minute. Assembly 14 isactuated by the specimen only to the extent necessary to control tensionon the specimen upon extending. 1

As best seen in FIG. 2 of the drawings, the inboard ends of a pair ofconnecting rods 1701-471) pass through apertures in the assembly 13 andattach thereto in a conventional manner. The rods 17a17b are journaledin cylindrical bearings 18a--18b, respectively, fixedly mounted in themid-portion of end panel 11. A cross head 19 (see FIG. 2) of a swivelbracket 20 is adapted to receive the outboard ends of rods 17a17b in aconventional manner.- The ratiomotor M heretofore referred to connectswith bracket 20 by a shaft 21 and a pin 22, respectively.

Referring again to FIGS. 1 and 2 of the drawings, collars 23a23b, or thelike, are detachably secured to p the tracks 15a--15b, respectively, asby set screws 24.

Compression springs 25a-25b are concentric about tracks 15a'15b, theoutboard ends of the springs 2551-- 2512 abut the inboard portions ofthe assembly 14- while the inboard ends of said springs abut the collars23a---- 23b. The position of collars 23a-23b are adjusted to regulatethe tension on the assembly 14 through the action of springs 25a25b.Leather washers Zea-26b positioned on the tracks 15a15b, respectively,abut the outboard ends of the assembly 14 and absorb shock between theassembly 14 and a spacer bar 27 which slidably mounts on the tracks15:1-1517.

The inboard end of a spindle 28a passes through an aperture in bar 27and connects thereto in a conventional manner. Spindle 28a passesthrough a bushing 28b incorporated in the end panel 12'and terminates ina knob 28. Application of a torque to'the knob 28 controls thedisplacement of the assembly 14. In a preferred embodiment of theinvention,'the maximum displacement of the assembly 13 is approximately1.5 inches whereas that of assembly 14 varies within the limits of 0.0to 0.5 inch.

As best seen in FIG. 1 of the drawings, clamp assemblies 29-30 areremovably mounted on horizontal extensions 13c1 4c, respectively, of theassemblies 13 -14. The extensions 13c-14c are integral with the lowerportion of the respective assemblies 13-14. The outboard ends of anoncorrosive metallic strip 29a of the assembly 29 are drilled to clearbolts 2% which screwably insert into the extension 13c. A rectangularspacer 23c corresponding to the shape of the strip 29a is also drilledto pass the bolts 2%. Wing nuts 29d, or the like, attach to the upperportions of the bolts 29b to secure one end of the specimen S betweenthe strip 29a and the spacer 290, respectively. Likewise, the other endof the specimen S is secured between strip 30a and spacer 39c by wingnuts 30d or the like placed on bolts 3012, respectively.

A wetting device, best seen in FIG. 1 of the drawings, consists of acylindrical pump'type plunger 51 suspended vertically in a watercontainer 32. A circular perforated plate 31a, integral with the sidewall portions of plunger 31, is made resilient by spring 33. Plate 311;maintains contact with the specimen S at every stage of the cycle. Theplate 31a is preferably countersunk at the center (see FIGS. 1 and toretain water momentarily, and is bevelled at the edge to prevent toosevere scufling of the specimen.

The plunger 31 slidably inserts into a recess 34 in the neck 32a ofcontainer 32. An orifice 35 in the lower surface 34a of recess 34 admitswater at the rate of approximately 450 to 500 ml. per hour, said flow iscontrolled by a valve 36a in the inlet pipe 36. On bending, as shown inthe broken line portions of FIGS. 1 and 5 of the drawings, the specimenS forces the plunger 31 downward into the recess 34 against the force ofSpring 33 which abuts the surface 34a. A pumping action results fromthis reciprocal motion. Water entering through the open bottom portionof the plunger 31 is forced up and through the perforations in the plate31a producing a spray on the under surface of the specimen, the waterbeing forced out in spurts rather than as a continuous flow. As a resultof the constant contact of the plate 31a with the lower surface of thespecimen S, the plate 31a serves as a mild abrader as well as a terminalin the electrical circuit hereinafter to be described. The plunger 31tends to rotate to a certain degree as the specimen is unbent in thecycle, thereby giving an abrasive effect that simulates conditions towhich the sole of a shoe is subjected when worn.

In a preferred embodiment of the invention, and as best seen in FIG. 1of the drawings, the container 32 is of stepped configuration. Channels37a-37b provided on the surfaces 32b-32c of container 32 conduct theunused water by way of conduits 3811-38!) to an outlet conduit 38. Thelower terminal of the electronic device hereinafter to be described maybe conveniently attached to the container 32 or inserted into the recess34, respectively, in a conventional manner.

The top terminal of the electronic device (see FIG. 1) consists of aspring-loaded presser foot 40, rectangular in shape, with its bottomsurface curved to conform with the crease in the bent specimen (see FIG.5). The presser foot 46 slidably inserts in an extension 42a of housing42. Said foot 40 maintains contact with the top (dry) surface of thespecimen S at every stage of the flexing cycle by the action of thespring 41 extending between presser foot 40 and the top, inside portionof the housing 42. The outboard end of the housing 42 is fixedly securedto the assembly 14 by a pillow block 43 of insulating material such aLucite or the like, as'best seen in FIG. 2 of the drawings. In apreferred embodiment of the invention, the housing 42 is of hollowtubular form and constructed of an electrical conducting material. Anelectrical lead 44a connects to the housing 42 in a conventional manner.

The foot 40 tends to revolve to-and-fro at an angle of about withinhousing extension 42a as the specimen is unbent. This movement isimportant because water may penetrate the specimen in an area outside ofthe crease as well as in the center of the crease and the limitedrotation of the presser foot permits the detection of the 4: end pointover such an area. Penetration points are found to occur over a greaterarea for untreated specimens than for treated specimens as hereinafterto be described.

As diagrammatically illustrated in FIG. 1 of the drawings, leads 44a44bconnect with an end point indicator 45 such as is well known to the art.As heretofore described one terminal of the lead 44:! attaches to thepresser foot 40 through housing 42, the other terminal of said lead 44aconnects with the end point indicator 45. Lead 44b connects plunger 31with the indicator 45. When water penetration of the specimen undergoingevaluation occurs, the external electrical circuit is completed therebyenergizing a control circuit within indicator 45 to cut off thereferred-to ratiomotor. The indicator 45 also includes an electricaltimer whereby time is recorded for both the beginning and termintaion ofthe testing process.

FIG. 5 of the drawings diagrammatically illustrates a leather specimen Sin both the unflexed and the flexed positions, wherein the flexedposition is represented by broken line portions. It will be observedfrom FIG. 1 of the drawings that the specimen is flexed so that thecrease is perpendicular to the longitudinal axis of the apparatus andthe convex surface is below the plane of the applied force. The originalshape of the specimen is not fully restored when the assemblies 13 14return to their original positions due to the stiffness of the leatherand to the pressure applied by the presser foot 40.

Specimens used for the water penetration tests on the apparatus of FIG.1 were 3 by 6 inches, however, specimens having various widths or a halfsole of conventional width can be tested on the device. Sizes under 2 /2inches in width are unsatisfactory, however, because water frequentlyescapes around the edges and makes contact with the top terminal of theindicator 45, especially when the resistance of the specimen topenetration is very great.

To clamp the specimen to the apparatus, the assemblies 131 are set about4 /2 inches apart, therefore the specimen S should have a minimum lengthof 6 inches to as sure proper clamping. A separation of 4 /2 inchesbetween the assemblies 13-14 produces an angle of bend of approximatelyIt is understood, of course, that the distance between the assemblies 13and 14 may be varied to produce the desired angle of bend. Also, it isoften necessary to adjust said assemblies to compensate for thethickness and stiffness of the specimen.

Commercial sole leather was used to obtain the data illustrated in FIGS.3 and 4 of the drawings. A group of specimens, prepared at the NationalBureau of Standards Leather Laboratory, includes untreatedvegetabletanned crust, impregnated crust and regular finished soleleather. Specifically, as illustrated in FIGS. 3 and 4 of the drawings,untreated chrome-retanned crust leather is designated by the referenceletter A, untreated vegetable-tanned crust leather by B, C designatesthe flesh side of untreated vegetable-tanned finish leather, Drepresents the grain side of said untreated vegetable-tanned finishleather and G designates treated (impregnated) vegetable-tanned crustleather. The specimen E was prepared with an Oronite treatment, Oronitebeing a trade name for a blend of a group of low molecular weightpolybutenes obtained from the Oronite Chemical Company. The numerals 1and 2 in FIG. 3 of the drawings designate the flexed and unflexedspecimens, respectively. The specimens C, D, E, and G, as illustrated inFIG. 4, were cut from untested parts of the corresponding specimens inFIG. 3 and submitted to a static water penetration testing procedurehereafter to be described. Prior to testing, the specimens utilized toobtain the data shown in FIGS. 3 and 4 were conditioned in an atmosphereof 72 F. and 50% relative humidity.

In FIG. 3 of the drawings, the percentage of water absorbed by theflexed and unflexed specimens A, B, C, D, and E is plotted against thetime of exposure in minutes.

The results show the influence of flexing by the increase in the amountof water absorbed during flexing in comparison with that absorbed by theunflexed specimens. It will be noted that the rate of absorption isfairly steady for each type of leather. The chrome-retanned leatherabsorbs the greatest amount of Water and shows a tendency to reachequilibrium at a greater rate than the other types of leather.Furthermore, improvement due to impregnation can be seen in comparingthe results for the treated leather with the untreated leather. Theflesh side of the untreated vegetable-tanned finished leather isintermediate and absorbs a greater amount of water than the grain side,the more porous sponge-like form of the flesh side being responsible forthe lower resistance to water.

The curves illustrated in FIG. 4 are typical water absorption curves forleather tested by the standard immersion method described in FederalSpecification KK-L- 311a. The results indicate that the rate of Waterabsorption for specimens immersed in water is greatest during the first30 minutes of exposure in comparison to the steady rate of absorptionshown by the results of FIG. 3. The resistance to water peneration underdynamic and static conditions is given in the following tabulation:

TABLE I Resistance to Water Penetration Under Dynamic and StaticConditions It is evident upon inspection of the results of Table I thatflexing increases the rate of penetration and the rate of absorption.Flexing the leather causes a pumping action, heretofore described, whichis partially responsible for the rapid penetration rate. During thetesting procedure it was observed that the water appears to enter thevoids of the leather as the specimen is bent and is forced through thevoids as the specimen is unbent. Penetration is generally detectedduring the return of the reciprocating assembly 13 to its originalposition. The results of Table I also amplify the findings illustratedin FIGS. 3 and 4 of the drawings.

Other test results indicate that the logarithm of the number of flexesto penetration is a direct function of the thickness of the leather.Also, the rate of water penetration and water absorption depends uponthe location of the specimen on the leather bend.

It will be apparent that the embodiments shown are only exemplary andthat various modifications can be made in construction and arrangementwithin the scope of invention as defined in the appended claims.

What is claimed is:

1. A device for testing the resistance of a test specimen to liquidpenetration comprising a base, panel members mounted on said base, trackmeans connecting said panel members, a test specimen, first and secondclamp means slidably mounted on said track means and securing said testspecimen, drive means for reciprocally moving said first clamp means andthereby flexing said test specimen, a liquid container, and pump meansadjacent one side of said test specimen for directing liquid from saidcontainer against said one side of said test specimen, said pumpmeans-being actuated by flexure of said test specimen thereagainstwhereby said test specimen is simultaneously wetted and abraded by saidpump means.

2. The invention of claim 1 including means to indicate the liquidpenetration of said specimen.

3. The invention of claim 1 including an endpoint indicator, anelectrical circuit connecting with said indicator and includingelectrodes attached to the opposite sides of said test specimen, saidelectrical circuit being completed through the liquid penetrating saidtest specimen.

4. The invention of claim 2 including means to deactivate said drivemeans and record the time of the liquid penetration of said specimen.

5. A device for testing the water penetration of a sole leather specimencomprising a base, first and second panel members mounted on said base,track means connecting said first and second panel members, first andsecond specimen clamping means slidably mounting on said track means,said first clamping means being reciprocally driven by a ratiomotor, awater bath, a spring biased plunger adjacent said leather specimen,means for directing water from said bath against said test specimen andmeans to deactivate said ratiomotor upon water penetration of saidleather specimen.

6. Apparatus for testing the water penetration of sole leathercomprising a base, first and second end panels connecting to said base,first and second track members connecting said first and second endpanels, first and second clamp means for securing said sole leather,said first and second clamp means slidably mounted on said first andsecond track members, said first clamp means positioned in proximity tosaid first end panel and said second clamp means positioned adjacentsaid second end panel, drive means to reciprocally move said first clampmeans,

means to adjustably position said second clamp means,

a liquid container, spring biased plunger means adjacent the lowersurface of said sole leather specimen, means for directing water againstsaid specimen and electrical means to indicate the water penetration ofsaid specimen.

References Cited in the file of this patent UNITED STATES PATENTS1,518,806 Mahannah Dec. 9, 1924 2,012,762 Kern Aug. 27, 1935 2,545,281Hunt Mar. 13, 1951 2,719,429 Hopton Oct. 4, 1955 OTHER REFERENCESPublication: Journal Am. Leather Chemists Assoc, article by Clarke etal., Sept, 1954, pages 624-629. (Copy in 73-100.)

